The quark contents of the following particles are: the beauty hyperon $A_b$ $=u d b$, the charmed meson $D^0=c \bar{u}$, the beauty mesons $B^{+}=u \bar{b}, B^{-}=\bar{u} b$ and $B^0=d \bar{b}$. Which of the following reactions are allowed? (a) $\pi^{-} p \rightarrow D^0 A_b$, (b) $\pi^{-} p \rightarrow B^0 A_b$, (c) $\pi^{-} p \rightarrow B^{+} A_b \pi^{-}$, (d) $\pi^{-} p \rightarrow B^{-} A_b \pi^{+}$, and (e) $\pi^{-} p \rightarrow B^{-} B^{+}$.